Friction agitation welding, and in particular friction-stir welding (FSW), is a solid-state joining process that uses a bobbin tool to join two abutting plate-shaped work pieces. Heat is generated between the tool and material that produces a very soft region near the bobbin tool. Then, the two pieces of metal mechanically intermix so that the softened metal can be joined using mechanical pressure applied by the bobbin tool. It is primarily used on aluminum and on structures that need superior weld strength without a post weld heat treatment. It is applicable in aircraft construction for longitudinally or circumferentially joining large parts as, for example, fuselage shells or fuel tanks.
US 2013/334289 A1 discloses a movable joining device for connecting structural components of an aircraft. The joining means is moveably arranged on a guiding device situated on the outside of the structural components so as to fixedly connect joining edges of the structural components positioned adjacent to each other. The joining means includes a welding unit that can move on a rail-like guiding device and is equipped with a special bobbin tool for friction stir welding.
US 2014/034711 A1 discloses a friction agitation welding process, wherein a rotating bobbin tool is moved along a weld between two plate-shaped work pieces, exerting a first and a second contact pressing force on first and second sides, respectively, and wherein the bobbin tool is subjected to an additional axial force during its movement along the weld to plastically deform the area of the created welding seam such that the welding seam is pressed towards one side of the plate-shaped work pieces while forming a welding seam elevation protruding opposite from the work piece surface.
However, a need still exists for an improved movable backing system to precisely clamp plate-shaped work pieces for friction agitation welding.